Question

Give reason for the following

(i) High reverse voltage do not appear across a LED.

(ii) Sunlight is not always required for the working of a solar cell.

(iii) The electric field, of the junction of a Zener diode, is very high even for a small reverse bias voltage of about 5 V

Answer 1

(i) It is because reverse break down voltage of LED is very low i.e., nearly 5 V.

(ii) Because solar cell can work with any light whose photon energy is more than the band gap energy.

(iii) The heavy doping of p and n sides of p-n junction, makes the depletion region very thin,,hence for a small reverse bias voltage, electric field is very high.